Fianna Fail's jobs spokesperson Willie O'Dea has said Enterprise Minister Richard Bruton must "act immediately" to reassure 200,000 low paid workers around the country.
It follows the High Court ruling that the system for setting minimum wages is unconstitutional.
People already under the Joint Labour Committee system will not have their pay changed, but those who take up jobs or have new contracts drawn up are expected to face lower rates.
Mr O'Dea said: "The minister will have access to the legal advice of the Attorney General and anybody else he wants to consult, but I would ask him to act immediately.
"There is a good deal of anxiety out there, there is a dangerous gap. The narrower that gap is the better."